1. Field of the Invention
The present invention relates to a receiver for a broadcast system in which analog broadcast signals and digital broadcast are broadcast signals in adjacent frequency bands.
2. Description of the Related Art
In the present AM broadcast and the FM broadcast, the processing of elements to be broadcast is being digitized, however, the broadcast itself is based on an analog system. However, if the broadcast is digitized, an additive data service such as supply of broadcast having high sound quality can be performed. The movement of the digitalization of the broadcast itself is being activated because of enhancement of a frequency using efficiency, etc.
However, in order to receive a digital broadcast, a digital broadcast receiver is necessarily newly required in place of an analog broadcast receiver which has been hitherto used. Therefore, it is required to smoothly shift from the analog broadcast to the digital broadcast with no resistance, and it is also required that the analog broadcast and the digital broadcast are allowed to coexist during the shift period.
A broadcast system of enabling the coexistence is generally called as xe2x80x9cIBOC (In Band On Channel) systemxe2x80x9d, and the coexistence of the analog broadcast and the digital broadcast can be implemented by setting the analog broadcast and the digital broadcast in such a frequency arrangement as shown in FIG. 1A, for example.
That is, in FIG. 1A, reference character SA represents a broadcast wave signal (FM signal) of the hitherto-used analog FM broadcast, and the carrier frequency thereof is represented by fRX. When the broadcast wave signal of the digital broadcast is allowed to coexist with the analog broadcast wave signal SA, the broadcast wave signals SD, SD of the digital broadcast are disposed so as to be adjacent to both ends of the frequency band of the broadcast wave signal SA.
However, in this case, only any one of the broadcast wave signals SD, SD may be provided. Further, the program content based on the broadcast wave signal SD is generally set to be identical to the program content based on the analog broadcast wave signal SA. Further, in the future, the analog broadcast wave signal SA will be stopped to perform the broadcast with only the digital broadcast wave signal SD, or the broadcast wave signal SA will be used for the digital broadcast. The shift from the analog broadcast to the digital broad is estimated to be established over ten years to fifteen years.
Accordingly, when a listener supports the above coexistence, the listener needs a receiver being operatable before and after the shift period, or a receiver for both the broadcasts which can receive the analog broadcast and the digital broadcast.
The present invention aims to enable reception of digital broadcast wave signals without making a great modification to a hitherto-used reception circuit for receiving analog broadcast wave signals, and also to suppress undesired power consumption.
Therefore, according to the present invention, there is provided a receiver for a broadcasting system in which the broadcast wave signal of an analog broadcast and the broadcast wave signal of a digital broadcast are broadcast in adjacent frequency bands, characterized by comprising:
a reception circuit for receiving the broadcast wave signal of the analog broadcast and outputting an audio signal based on the analog broadcast;
a digital demodulation circuit for digitally demodulating an intermediate frequency signal obtained in the reception circuit when the broadcast wave signal of the digital broadcast is received, and outputting an audio signal based on the digital broadcast;
a first detection circuit for detecting that the broadcast wave signal of the analog broadcast is received;
a second detection circuit for detecting that the broadcast wave signal of the digital broadcast is received; and
a control circuit for controlling supply of an operating power source voltage to the digital demodulation circuit, wherein the digital demodulation circuit is supplied with the operating power source voltage by the control circuit only when the first detection circuit detects the broadcast wave signal of the analog broadcast and the second detection circuit detects the broadcast wave signal of the digital broadcast at a station-selection time.
In the above receiver, each of the first and second detection circuit may include a circuit for detecting whether the reception is performed at a signal intensity above a predetermined level.
The above receiver may further include display means which is turned on to indicate that the broadcast wave signal of the analog broadcast or the broadcast wave signal of the digital broadcast is received, wherein the turn-on state of the display means is made different between when the broadcast wave signal of the analog broadcast is received and when the broadcast wave signal of the digital broadcast is received.
The above receiver may further include display means which is turned on to indicate that the broadcast wave signal of the analog broadcast or the broadcast wave signal of the digital broadcast is received, wherein the turn-on state of the display means is made different in accordance with whether the broadcast wave signal of the digital broadcast is received or not.
The above receiver may further include display means which is turned on to indicate that the broadcast wave signal of the analog broadcast or the broadcast wave signal of the digital broadcast is received, wherein the turn-on state of the display means is made different on the basis of the output of the first detection circuit and the output of the second detection circuit.
According to the present invention, there is also provided a receiver for a broadcasting system in which the broadcast wave signal of an analog broadcast and the broadcast wave signal of a digital broadcast are broadcast in adjacent frequency bands, characterized by comprising:
a reception circuit for receiving the broadcast wave signal of the analog broadcast and outputting an audio signal based on the analog broadcast;
a digital demodulation circuit for digitally demodulating an intermediate frequency signal obtained in the reception circuit when the broadcast wave signal of the digital broadcast is received, and outputting an audio signal based on the digital broadcast;
a first detection circuit for detecting that the broadcast wave signal of the analog broadcast is received;
a second detection circuit for detecting that the broadcast wave signal of the digital broadcast is received; and
a control circuit for controlling the supply of an operating power source voltage to the digital demodulation circuit, wherein the digital demodulation circuit is provided with a synchronous flag for representing establishment of synchronization when the synchronization is established in the digital demodulation circuit; the digital demodulation circuit is supplied with the operating power source voltage by the control circuit when the first detection circuit detects the broadcast wave signal of the analog broadcast and the second detection circuit detects the broadcast wave signal of the digital broadcast at a station-selection time; and the supply of the operating power source voltage to the digital demodulation circuit is continued when the synchronous flag indicates it within a predetermined time from the supply of the operating power source voltage that the synchronization is established in the digital demodulation circuit, and the supply of the operating power source voltage to the digital demodulation circuit is stopped when the synchronous flag does not indicate that the synchronization is established in the digital demodulation circuit.
Accordingly, the power is consumed in the digital processing circuit only when the digital broadcast is received.